Angiographic catheters are very small but long thin-walled tubes that are inserted into the human vascular system for diagnostic or therapeutic purposes. At the present time, almost all such catheters have an end-hole at the distal end so that the catheter can be passed over and guided by a wire which has been inserted into the vascular system through a hollow needle placed in a blood vessel. Also, because these catheters are open at both ends to allow passage over the guidewire, one catheter can be exchanged for another by replacing the wire and withdrawing the catheter over the wire.
When used in diagnostic procedures, the primary purpose of these catheters is to allow injection of radiopaque contrast material into the blood stream so as to produce an image of the blood vessel (an angiogram) on x-ray film. During the process of diagnostic angiography, the contrast medium is usually injected at a rapid rate using a power injector, and the contrast medium is forcefully discharged from the distal end-hole of the catheter creating a jet effect. This produces undesirable recoil of the catheter and can also produce a dangerous complication, subintimal injection of the contrast medium, in which the jet tunnels into the wall of the blood vessel sometimes resulting in acute occlusion of the vessel.
To minimize the undesirable effect of recoil and the potential complication of subintimal injection, some early catheter designs had sealed distal ends with side-holes near the distal end to allow injection of the contrast medium into the blood vessel laterally and symmetrically thereby reducing subintimal injections. Of course, with the sealed distal end, these catheters cannot be inserted into a blood vessel over a guidewire, and therefore this design is not widely used. Most catheters presently used for rapid flush angiography are configured with a circular loop or "pigtail" at the distal end. Although the end-hole is open, these pigtail type catheters are provided with side-holes through which approximately 40% of the contrast medium is discharged. Although the looped end of the catheter decreases somewhat the chance of subintimal injection, the open end-hole still allows approximately 60% of the contrast medium to exit the end-hole in a strong jet. During left ventriculography, this jet has been associated with the production of ventricular arrhythmias which can be dangerous to the patient and which can lessen the accuracy of the acquired physiologic data. To overcome the limitations of the pigtail catheter in cardiac angiography, various modifications have been attempted to the pigtail configuration, such as a multiple loop configuration or formation of a bend at an acute angle in the distal portion of the catheter. However, these modifications have not satisfactorily alleviated the problems associated with the use of any catheter which has an open end-hole.
Moreover, when catheters of this type are used during abdominal aortography, it is sometimes desirable to have the contrast medium injected in a lateral fashion to opacify the renal arteries which arise at right angles to the abdominal aorta. The pigtail catheter, including known modifications of it, tends to inject the contrast medium in a superior direction through the superiorally directed end-hole. This produces the undesirable effect of filling the blood vessels superior to the renal arteries which can obscure visualization of the anatomic structures being observed.
There is therefore a need for a catheter which can be inserted into the vascular system by passing it over a guidewire but which catheter will have the advantages of a closed-end catheter.